Shock absorber oil composition

ABSTRACT

A shock absorber oil composition of the invention includes a base oil: (A) at least one of phosphate, amine phosphate salt, phosphite and amine phosphite salt; (B) an amide compound; and (C) an N-substituted derivative of sarcosine.

TECHNICAL FIELD

The present invention relates to a shock absorber oil composition.

BACKGROUND ART

As a shock absorber used for effectively absorbing vibration, forinstance, a hydraulic shock absorber is widely used in an automobile orthe like. The shock absorber is a functional component that plays animportant role for vehicle handling, stability and ride quality,especially for ride quality.

Accordingly, there has been proposed a technology for particularlyimproving ride quality during travel on an expressway by improvingfriction characteristics of a shock absorber oil composition used in ashock absorber (Patent Literature 1).

CITATION LIST Patent Literature(s)

Patent Literature 1: JP-A-2000-119677

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, the shock absorber oil composition disclosed in PatentLiterature 1 transmits a rough vibration to a vehicle body during travelat a low speed, which may cause an insufficient ride quality.

An object of the invention is to provide a shock absorber oilcomposition providing an excellent ride quality during travel.

Means for Solving the Problems

In order to solve the above-mentioned problem, according to theinvention, a shock absorber oil composition as follows is provided.

Specifically, a shock absorber oil composition according to an aspect ofthe invention includes: a base oil: a component (A) that is at least oneof phosphate, amine phosphate salt, phosphite and amine phosphite salt;a component (B) that is an amide compound; and a component (C) that isan N-substituted derivative of sarcosine.

In the shock absorber oil composition according to the above aspect ofthe invention, it is preferable that the component (A) has an alkylgroup or an alkenyl group, and the alkyl group or the alkenyl group has12 to 20 carbon atoms.

In the shock absorber oil composition according to the above aspect ofthe invention, it is preferable that the component (B) has an alkylgroup, and the alkyl group has 12 to 20 carbon atoms.

In the shock absorber oil composition according to the above aspect ofthe invention, it is preferable that an N-substituent in the component(C) has 12 to 20 carbon atoms.

In the shock absorber oil composition according to the above aspect ofthe invention, it is preferable that a content of the component (A) isin a range of 0.1 mass % to 1 mass % of a total amount of thecomposition, a content of the component (B) is in a range of 0.1 mass %to 1 mass % of the total amount of the composition, and a content of thecomponent (C) is in a range of 0.1 mass % to 1 mass % of the totalamount of the composition.

According to the above aspect of the invention, a shock absorber oilcomposition providing an excellent ride quality during travel can beprovided.

DESCRIPTION OF EMBODIMENT(S)

A shock absorber oil composition of the invention (hereinafter, alsoreferred to as “the composition”) is provided by blending to a base oil:(A) at least one of phosphate, amine phosphate salt, phosphite and aminephosphite salt; (B) an amide compound; and (C) an N-substitutedderivative of sarcosine. The composition of the invention will bedescribed in detail below.

The base oil used in the composition may be a mineral lubricating baseoil or a synthetic lubricating base oil. The kind of the lubricatingbase oil is not particularly limited but may be suitably selected fromany mineral oil and synthetic oil that have been conventionally used asa base oil of a shock absorber oil.

Examples of the mineral lubricating base oil include a paraffinicmineral oil and a naphthenic mineral oil. Examples of the lubricatingbase oil include polybutene, polyolefin, polyol ester, diacid ester,phosphate, polyphenyl ether, polyglycol, alkyl benzene, and alkylnaphthalene. Examples of the polyolefin include an α-olefin homopolymerand an α-olefin copolymer. One of the above base oils may be singularlyused or a combination of two or more thereof may be used.

A component (A) used in the composition is at least one of phosphate,amine phosphate salt, phosphite and amine phosphite salt. The component(A) preferably has an alkyl group or an alkenyl group. The alkyl groupor alkenyl group preferably has 12 to 20 carbon atoms in terms of afriction coefficient between metals in the composition Examples of thealkyl group include a lauryl group, myristyl group, cetyl group, andstearyl group. The alkenyl group is exemplified by an oleyl group.Examples of the component (A) include acidic phosphate of alcohol (e.g.,lauryl alcohol and oleyl alcohol) and phosphoric acid, an amine salt ofthe acidic phosphate, phosphite of alcohol (e.g., lauryl alcohol andoleyl alcohol) and phosphorous acid, and an amine salt of the phosphite.One of the components (A) may be singularly used or a combination of twoor more thereof may be used.

A content of the component (A) is not particularly limited, but ispreferably in a range of 0.1 mass % to 1 mass % of a total amount of thecomposition, more preferably in a range of 0.3 mass % to 0.7 mass %.When the content of the component (A) is excessively small, thecomposition tends to exhibit a high friction coefficient between metalsduring travel at a low speed. On the other hand, when the content of thecomponent (A) is excessively large, an undissolved portion of thecomponent (A) is left, which may not always provide advantageous effectsfor the content.

A component (B) used in the composition is an amide compound. Thecomponent (B) preferably has an alkyl group. The alkyl group preferablyhas 12 to 20 carbon atoms in terms of the friction coefficient betweenmetals in the composition. Examples of the component (B) include lauricacid amide, myristic acid amide, palmitic acid amide and stearic acidamide. One of the components (B) may be singularly used or a combinationof two or more thereof may be used.

A content of the component (B) is not particularly limited, but ispreferably in a range of 0.1 mass % to 1 mass % of the total amount ofthe composition, more preferably in a range of 0.3 mass % to 0.7 mass %.When the content of the component (B) is excessively small, thecomposition tends to exhibit a high friction coefficient between metalsduring travel at a low speed. On the other hand, when the content of thecomponent (B) is excessively large, an undissolved portion of thecomponent (B) is left, which may not always provide advantageous effectfor the content.

A component (C) used in the composition is an N-substituted derivativeof sarcosine. An N-substituent in the component (C) preferably has 12 to20 carbon atoms in terms of a friction coefficient between metals in thecomposition. Examples of the N-substituent include an alkyl group and analkenyl group. Examples of the component (C) include N-oleylsarcosine(N-oleoylsarcosine), N-lauroylsarcosine, N-myristoylsarcosine, andN-palmitoylsarcosine. One of the components (C) may be singularly usedor a combination of two or more thereof may be used.

A content of the component (C) is not particularly limited, but ispreferably in a range of 0.1 mass % to 1 mass % of the total amount ofthe composition, more preferably in a range of 0.3 mass % to 0.7 mass %.When the content of the component (C) is excessively small, thecomposition tends to exhibit a high friction coefficient between metalsduring travel at a low speed. On the other hand, when the content of thecomponent (C) is excessively large, an undissolved portion of thecomponent (C) is left, which may not always provide advantageous effectfor the content.

The composition satisfying the following conditions (i) to (iii) can beobtained by blending the components (A), (B) and (C) to the base oil.

(i) A friction coefficient between metals at a speed of 10 mm/s (ahigh-speed intermetal friction coefficient μ) is preferably 0.12 orless, more preferably in a range of 0.1 to 0.115.(ii) A friction coefficient between metals at a speed of 0.3 mm/s (alow-speed intermetal friction coefficient μ) is preferably 0.11 or less,more preferably in a range of 0.8 to 0.1.(iii) A ratio between the friction coefficients between metals (thelow-speed intermetal friction coefficient μ/the high-speed intermetalfriction coefficient μ) is preferably 0.95 or less, more preferably in arange of 0.8 to 0.9.

When the high-speed intermetal friction coefficient μ, the low-speedintermetal friction coefficient μ, and the ratio between the frictioncoefficients between metals (low-speed intermetal friction coefficientμ/high-speed intermetal friction coefficient μ) satisfy the aboveconditions, a movement of expansion and contraction of the shockabsorber becomes smooth. Accordingly, the shock absorber can efficientlyabsorb vibration during travel (particularly during travel at a lowspeed). Thus, it is speculated that a shock absorber oil compositionproviding an excellent ride quality during travel is obtainable.

A measuring method of the friction coefficient between metals at thespeed of 10 mm/s (high-speed intermetal friction coefficient μ) and thefriction coefficient between metals at the speed of 0.3 mm/s (low-speedintermetal friction coefficient μ) will be shown in a later-describedExample.

The composition may further contain various additives below as long asthe advantageous effects of the invention are not impaired.Specifically, a viscosity index improver, pour point depressant,detergent dispersant, antioxidant, antiwear agent/extreme pressureagent, friction reducing agent, metal deactivator, rust inhibitor,surfactant/anti-emulsifier, antifoaming agent, anticorrosive agent,friction modifier, oiliness agent, acid scavenger and the like may besuitably blended to be used.

Examples of the viscosity index improver include a non-dispersedpolymethacrylate, dispersed polymethacrylate, olefin copolymer,dispersed olefin copolymer and styrene copolymer. As a mass averagemolecular weight of the viscosity index improver, for instance,dispersed and non-dispersed polymethacrylates preferably each have amass average molecular weight in a range of 5000 to 300000. The olefincopolymer preferably has a mass average molecular weight in a range of800 to 100000. One of the viscosity index improvers may be singularlyused or a combination of two or more thereof may be used.

A content of the viscosity index improver is not particularly limited,but is preferably in a range of 0.5 mass % to 15 mass % of the totalamount of the composition, more preferably in a range of 1 mass % to 10mass %.

The pour point depressant is exemplified by polymethacrylate having amass average molecular weight in a range of 5000 to 50000. One of thepour point depressants may be singularly used or a combination of two ormore thereof may be used.

A content of the pour point depressant is not particularly limited, butis preferably in a range of 0.1 mass % to 2 mass % of the total amountof the composition, more preferably in a range of 0.1 mass % to 1 mass%.

As the detergent dispersant, an ashless dispersant and a metal-basedetergent may be used.

Examples of the ashless dispersant include a succinimide compound, aboron-based imide compound, and a Mannich dispersant. One of the ashlessdispersants may be singularly used or a combination of two or morethereof may be used. A content of the ashless dispersant is notparticularly limited, but is preferably in a range of 0.1 mass % to 20mass % of the total amount of the composition.

Examples of the metal-base detergent include alkali metal sulfonate,alkali metal phenate, alkali metal salicylate, alkali metal naphthenate,alkaline earth metal sulfonate, alkaline earth metal phenate, alkalineearth metal salicylate, and alkaline earth metal naphthenate. One of themetal-base detergents may be singularly used or a combination of two ormore thereof may be used. A content of the metal-base detergent is notparticularly limited, but is preferably in a range of 0.1 mass % to 10mass % of the total amount of the composition.

Examples of the antioxidant include an amine antioxidant, a phenolantioxidant, and a sulfur antioxidant. One of the antioxidants may besingularly used or a combination of two or more thereof may be used.

A content of the antioxidant is not particularly limited, but ispreferably in a range of 0.05 mass % to 7 mass % of the total amount ofthe composition.

The antiwear agent/extreme pressure agent is exemplified by a sulfurextreme pressure agent. Examples of the sulfur extreme pressure agentinclude an olefin sulfide, a sulfurized fat and oil, an ester sulfide,thiocarbonates, dithiocarbamates and polysulfides. One of the antiwearagents/the extreme pressure agents may be singularly used or acombination of two or more thereof may be used.

A content of the antiwear agent/the extreme pressure agent is notparticularly limited, but is preferably in a range of 0.1 mass % to 20mass % of the total amount of the composition.

Examples of the friction reducing agent include a fatty acid ester,fatty acid, aliphatic alcohol, aliphatic amine, and aliphatic ether.Specifically, the friction reducing agent includes at least one alkylgroup or alkenyl group having 6 to 30 carbon atoms in a molecule. One ofthe friction reducing agents may be singularly used or a combination oftwo or more thereof may be used.

A content of the friction reducing agent is not particularly limited,but is preferably in a range of 0.01 mass % to 2 mass % of the totalamount of the composition, more preferably in a range of 0.01 mass % to1 mass %.

Examples of the metal deactivator include a benzotriazole metaldeactivator, tolyltriazole metal deactivator, thiadiazole metaldeactivator, and imidazole metal deactivator. One of the metaldeactivators may be singularly used or a combination of two or morethereof may be used.

A content of the metal deactivator is not particularly limited, but ispreferably in a range of 0.01 mass % to 3 mass % of the total amount ofthe composition, more preferably in a range of 0.01 mass % to 1 mass %.

Examples of the rust inhibitor include petroleum sulfonate, alkylbenzenesulfonate, dinonylnaphthalene sulfonate, alkenyl succinic ester andmultivalent alcohol ester. One of the rust inhibitors may be singularlyused or a combination of two or more thereof may be used.

A content of the rust inhibitor is not particularly limited, but ispreferably in a range of 0.01 mass % to 1 mass % of the total amount ofthe composition, more preferably in a range of 0.05 mass % to 0.5 mass%.

The surfactant/anti-emulsifier is exemplified by a polyalkylene glycolnon-ionic surfactant. Specific examples of thesurfactant/anti-emulsifier include polyoxyethylenealkylether,polyoxyethylenealkylphenylether, and polyoxyethylenealkylnaphthylether.One of the surfactants/anti-emulsifiers may be singularly used or acombination of two or more thereof may be used.

A content of the surfactant/anti-emulsifier is not particularly limited,but is preferably in a range of 0.01 mass % to 3 mass % of the totalamount of the composition, more preferably in a range of 0.01 mass % to1 mass %.

Examples of the antifoaming agent are silicone oil, fluorosilicone oil,and fluoroalkylether. One of the antifoaming agents may be singularlyused or a combination of two or more thereof may be used.

A content of the antifoaming agent is not particularly limited, but ispreferably in a range of 0.005 mass % to 0.5 mass % of the total amountof the composition, more preferably in a range of 0.01 mass % to 0.2mass %.

Examples of the anticorrosive agent include a benzotriazoleanticorrosive agent, a benzimidazole anticorrosive agent, abenzothiazole anticorrosive agent and a thiadiazole anticorrosive agent.One of the anticorrosive agents may be singularly used or a combinationof two or more thereof may be used.

A content of the anticorrosive agent is not particularly limited, but ispreferably in a range of 0.01 mass % to 1 mass % of the total amount ofthe composition.

Examples of the friction modifier include an organic molybdenumcompound, fatty acid, higher alcohol, fatty acid ester, oils and fats,amine, and ester sulfide. One of the friction modifiers may besingularly used or a combination of two or more thereof may be used.

A content of the friction modifier is not particularly limited, but ispreferably in a range of 0.01 mass % to 10 mass % of the total amount ofthe composition.

Examples of the oiliness agent include aliphatic monocarboxylic acid,polymerized fatty acid, hydroxy fatty acid, and aliphatic monoalcohol.One of the oiliness agents may be singularly used or a combination oftwo or more thereof may be used.

A content of the oiliness agent is not particularly limited, but ispreferably in a range of 0.01 mass % to 10 mass % of the total amount ofthe composition.

As the acid scavenger, an epoxy compound may be used. Specific examplesof the acid scavenger include phenyl glycidyl ether, alkyl glycidylether, alkylene glycol glycidyl ether, cyclohexene oxide, α-olefin oxideand epoxidized soybean oil. One of the acid scavengers may be singularlyused or a combination of two or more thereof may be used.

A content of the acid scavenger is not particularly limited, but ispreferably in a range of 0.005 mass % to 5 mass % of the total amount ofthe composition.

EXAMPLE

The invention will be described in more detail below with reference toExamples and Comparatives. It should be noted that the invention is notlimited to the description of Examples and the like.

Examples 1 to 4 and Comparatives 1 to 2

Shock absorber oil compositions (sample oils) were prepared from thefollowing materials according to the blending composition shown inTable 1. Properties of the sample oils and actual ride quality wereevaluated according to the following methods.

(1) Friction Coefficient between Metals (at Low and High Speeds) andRatio Therebetween

Friction coefficients between metals were measured under the followingconditions using a reciprocating friction tester. A friction coefficientbetween metals at a speed of 10 mm/s (friction coefficient μ betweenmetals at a high speed) and a friction coefficient between metals at aspeed of 0.3 mm/s (low-speed intermetal friction coefficient μ) weremeasured. A ratio between the friction coefficients between metals(low-speed intermetal friction coefficient μ/high-speed intermetalfriction coefficient μ) was calculated.

-   Test Ball: SUJ2 steel ball-   Test Plate: SUJ2 steel plate-   Oil temperature: 60 degrees C.-   Load: 0.5 kgf-   Speed: 10 mm/s (at a high speed), 0.3 mm/s (at a low speed)

(2) Actual Ride Quality Test

Vehicles provided with shock absorbers using the sample oils wereprepared. Four drivers each conducted an actual ride quality test. Thedrivers respectively evaluated the vehicles on a five-point scale interms of ten items including a ride feeling (a good ride quality), ahardness feeling (a beat feeling (i.e., a feeling on the foot sole andthe hip when traveling on a cracked road surface and the like)), balance(a ride quality to keep the vehicle in balance), straight-runningstability and the like. The obtained points were averaged to provide anevaluation point of the actual ride quality test. The ride quality ismore superior as the point is higher.

-   Base Oil: Mineral oil (kinematic viscosity at 40 degrees C.: 8.02    mm²/s)-   Viscosity Index Improver: Polymethacrylate (weight average molecular    weight: 140000)-   Detergent Dispersant 1: Polybutenyl succinimide-   Detergent Dispersant 2: Calcium sulfonate-   Detergent Dispersant 3: Fatty acid amide (stearyl)-   Antiwear Agent 1: Acidic phosphate amine salt (oleyl)-   Antiwear Agent 2: Acidic phosphate amine salt (lauryl)-   Antiwear Agent 3: Phosphite (oleyl)-   Antiwear Agent 4: Phosphite (lauryl)-   Oiliness Agent: Oleyl sarcosine

TABLE 1 Example 1 Example 2 Example 3 Example 4 Comp. 1 Comp. 2 BlendingBase oil 94.88 94.88 94.88 94.88 94.88 94.88 Composition Viscosity indeximprover 2.20 2.20 2.20 2.20 2.20 2.20 (mass %) Detergent dispersant 1 —— — — 0.50 — Detergent dispersant 2 — — — — — 0.50 Component (B)Detergent dispersant 3 0.50 0.50 0.50 0.50 — — Component (A) Antiwearagent 1 0.50 — — — 0.50 0.50 Component (A) Antiwear agent 2 — 0.50 — — —— Component (A) Antiwear agent 3 — — 0.50 — — — Component (A) Antiwearagent 4 — — — 0.50 — — Component (C) Oilness agent 0.50 0.50 0.50 0.500.50 0.50 Other additives 1.42 1.42 1.42 1.42 1.42 1.42 Properties andFriction coefficient between metals @ 10 mm/s 0.107 0.110 0.110 0.1120.123 0.123 Evaluation Friction coefficient between metals @ 0.3 mm/s0.089 0.096 0.095 0.096 0.119 0.122 Ratio between friction coefficientbetween 0.832 0.873 0.864 0.857 0.967 0.992 metals Actual ride qualitytest 4.8 4.6 4.6 4.7 3.6 3.7

As is obvious from the results shown in Table 1, when the shock absorberoil compositions containing the components (A) to (C) were used (inExamples 1 to 4), the low-speed intermetal friction coefficient p,tended to be low while the ratio between the friction coefficientsbetween metals (low-speed intermetal friction coefficient μ/high-speedintermetal friction coefficient μ) tended to be small, whereby anexcellent ride quality during travel was confirmed.

In contrast, when the shock absorber oil compositions containing nocomponent (B) were used (in Comparatives 1 to 2), the low-speedintermetal friction coefficient μ was high while the ratio between thefriction coefficients between metals (low-speed intermetal frictioncoefficient μ/high-speed intermetal friction coefficient μ) was about 1,whereby a poor ride quality during travel was confirmed.

INDUSTRIAL APPLICABILITY

A shock absorber oil composition of the invention is suitable as a shockabsorber oil composition used for a shock absorber (e.g., monotube andmulti-tube types) of an automobile (e.g., a motorcycle and a four-wheelvehicle).

1. A shock absorber oil composition, comprising: a base oil; a component(A) which is at least one selected from the group consisting ofphosphate, amine phosphate salt, phosphite and amine phosphite salt; acomponent (B) which is an amide compound; and a component (C) which isan N-substituted derivative of sarcosine.
 2. The composition accordingto claim 1, wherein the component (A) has an alkyl group or an alkenylgroup, and the alkyl group or the alkenyl group has 12 to 20 carbonatoms.
 3. The composition according to claim 1, wherein the component(B) has an alkyl group, and the alkyl group has 12 to 20 carbon atoms.4. The composition according to claim 1, wherein the N-substituent inthe component (C) has 12 to 20 carbon atoms.
 5. The compositionaccording to claim 1, wherein, based on a total amount of thecomposition, a content of the component (A) is from 0.1 mass % to 1 mass%, a content of the component (B) is from 0.1 mass % to 1 mass %, and acontent of the component (C) is from 0.1 mass % to 1 mass %.